PCM5102 charge pump frequency

The PCM5102 is a nice I2S DAC. We use it in you HiFiBerry Mini DAC. It is easy to use, because it does not need a master clock and can run on a single 3.3V power supply. To generate a full 2Vrms signal, the chip uses an internal charge pump (with two external 2.2uF capacitors) to generate a negative power supply.

Unfortunately the datasheet gives no information about the switching frequency of the charge pump. But it’s not a secret. You can simply have a look on the voltage on the external capacitor. What do we see? Switching frequency is about 850kHz – way out of the audible frequency range.

Update 13.11.13: It seems, that the charge pump frequency depends on the sample rate. We’ve seen even charge pump frequencies above 1MHz.